I know this is a very old thread with a new reply, but I did want to say there are important differences in aftermarket glass (especially having been involved with glass production through work).

There are several companies out there making glass and not all are equal. Some of these companies are even OEM suppliers as well. But there are also budget brands with lower standards.

If you go to a reputable windshield shop, chances are they're using quality glass. But there's plenty of these bottom dollar shops (especially the ones offering you gift cards / kickbacks to have your insurance replacement done with them) that use the cheapest stuff they can get their hands on - which is how they can afford to replace your windshield, make a profit, and give you a bit too.

A few key areas of differences:
-Distortion / waviness. The glass has to be molded to the curved shape - poor tooling and a crumby process can make for localized distortion where its curved. Different companies have different standards for how much distortion theyll allow measured against a standardized grid pattern background.

-Transmissibility / haze. Even in an untinted window, 100% of the light doesnt come through - some is absorbed / reflected, especially in laminated glass. Using low quality inter layer adhesive can reduce the amount of light making its way through cleanly.

-FOD allowances - specs of dust, hair, bug pieces, etc trapped during the lamination process or during manufacture of the interlayer. Higher quality glass will tend to have more stringent QC (which tends to drive them to run a cleaner shop to avoid scrap).

-Thickness. Some people report aftermarket windshields breaking more easily - sometimes this is caused by them going a little thinner on the glass layers to save cost in raw materials and make the forming process easier.


If someone were truly worried about it, you can simply ask what brand your glass shop plans to use and do a quick google search. Its not particularly ambiguous which shops make the cheap junk.